Light emitting diode package and method for manufacturing same

ABSTRACT

An exemplary light emitting diode package includes a housing, and a light emitting unit received in the housing. The light emitting unit includes a first carbon nanotube layer, a plurality of spaced light emitting chips, and a second carbon nanotube layer. The light emitting chips are formed on the first carbon nanotube layer. The second carbon nanotube layer covers the light emitting chips.

BACKGROUND

1. Technical Field

The present disclosure relates to light emitting diode packages andmethods for manufacturing the same.

2. Description of Related Art

A typical light emitting diode package includes a light emitting chip,two electrodes attached to opposite surfaces of the light emitting chipand a housing for receiving the light emitting chip and the twoelectrodes. However, a material of the electrodes is generally metal,such as copper or gold. This decreases light emitting efficiency of thelight-emitting diode package.

Therefore, a light emitting diode package and a method for manufacturingthe same, which can overcome the above-mentioned problems, are needed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a light emitting diode package, accordingto a first exemplary embodiment.

FIG. 2 is a planar view of the light emitting diode package of FIG. 1.

FIG. 3 is an isometric and schematic view of a method for manufacturinga carbon nanotube film used in the light emitting diode package of FIG.1.

FIG. 4 is a flow chart of a method for manufacturing a light emittingdiode package, according to a second exemplary embodiment.

FIGS. 5 a to 5 h show schematic views of the method of manufacturing thelight emitting diode package of FIG. 4.

FIG. 6 is a sectional view of a light emitting diode package, accordingto a third exemplary embodiment.

FIG. 7 is a planar view of a light emitting diode package, according toa fourth exemplary embodiment.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, a light emitting diode package 20, accordingto a first exemplary embodiment, includes a housing 22, and a lightemitting unit 24 received in the housing 22.

The housing 22 may be made from polymethylmethacrylate (PMMA) or epoxyresin and protects the light emitting unit 24.

In this embodiment, the light emitting unit 24 emits a white light andincludes a light reflective layer 200, a first carbon nanotube (CNT)layer 202, a plurality of light emitting chips 204, a second CNT layer206, and a phosphor layer 208. The first CNT layer 202 is formed on thelight reflective layer 200. The plurality of light emitting chips 204are formed on the first CNT layer 202 in an array (see FIG. 2). Thesecond CNT layer 206 is transparent to visible light and covers thelight emitting chips 204. The phosphor layer 208 is formed on the secondCNT layer 206. The CNT layers 202, 206 serve as two electrodes of thelight emitting diode package 20.

The light reflective layer 200 is a silver reflective layer with athickness of about 20-25 microns. The light reflective layer 200 isconfigured for reflecting light toward a light emitting surface 24 a ofthe light emitting unit 24. This increases utilization rate of light.

Each light emitting chip 204 emits a blue light. The phosphor layer 208is a layer comprising yttrium aluminum garnet (YAG) crystal, such as anepoxy-resin layer comprising the YAG crystal. The light emitting chip204 emits the blue light with a wavelength of about 400-530 nanometers.The blue light excites the phosphor layer 208 to emit a yellow light.Then the blue light and the yellow light are mixed to form the whitelight. It is to be understood that, in alternative embodiments, thephosphor layer 208 may be made from other material rather than theepoxy-resin layer comprising the YAG crystal, and the light emittingchip 204 may emit a colored light to excite the phosphor layer 208 toemit other colored light. In further alternative embodiments, thephosphor layer 208 may be omitted, and then the light emitting diodepackage 20 emits light the same color as the light from the lightemitting chips 24.

The light emitting chip 204 includes a light outgoing surface 204 a anda bottom surface 204 c at opposite sides of the light emitting chip 204.The light emitting chip 204 further includes microstructures 204 bformed on the light outgoing surface 204 a. The first CNT layer 202 isformed on the bottom surface 204 c. An area of each light outgoingsurface 204 a is about 1 square millimeter (about 1 millimeter long byabout 1 millimeter wide). A thickness of the light emitting chip 204,i.e., measured from the bottom surface 204 c to the light outgoingsurface 204 a, is greater than about 200 microns.

In this embodiment, the microstructures 204 b formed on the lightoutgoing surface 204 a include a plurality of cone-shaped grooves 204 bdefined in the light outgoing surface 204 a. A depth of each groove 204b is about 3-10 microns. The microstructures 204 b can converge lightemitted from the corresponding light emitting chip 204 to enhancebrightness of the light emitting diode package 20.

When covering the light emitting chips 204, parts of the second CNTlayer 206 may be attached inside the grooves 204 b. This enhances acontact area between the second CNT layer 206 and the light emittingchips 204. Accordingly, a conductivity between the second CNT layer 206and the light emitting chips 204 can be enhanced.

The first and second CNT layers 202, 206 include (a) CNT film(s).Methods for making a CNT film may include a direct growth method, aflocculating method, a pressing method or a pulling method.

The direct growth method is used to grow CNT films directly on asubstrate.

The flocculating method for making a CNT film includes the followingsteps: adding a plurality of CNTs to a solvent to create a CNT flocculestructure in the solvent; separating the CNT floccule structure from thesolvent; and shaping the separated CNT floccule structure into the CNTfilm. The CNT film made by the flocculating method includes a pluralityof isotropic CNTs twisted with each other and disorderly distributedtherein.

The pressing method for making a CNT film includes the following steps:forming an array of CNTs on a substrate; and pressing the array of CNTsusing a compressing apparatus, thereby forming a CNT film. The CNT filmmade by the pressing method includes a plurality of CNTs aligned in oneor more directions.

In this embodiment, the pulling method is adopted to make the CNT film.

Referring to FIG. 3, in step (a), the pulling method includes thefollowing sub-steps: (a1) providing a CNT array 116, specifically, asuper-aligned CNT array 116, on a substrate 114; and (a2) pulling out aCNT film 118 from the CNT array 116 with a pulling tool 100 (e.g.,adhesive tape, pliers, tweezers, or another tool allowing multiple CNTsto be gripped and pulled simultaneously).

In step (a1), the method for making the super-aligned CNT array 116 onthe substrate 114 includes the following sub-steps: (a11) providing asubstantially flat and smooth substrate 114; (a12) forming a catalystlayer on the substrate 114; (a13) annealing the substrate 114 with thecatalyst layer thereon at a temperature ranging from 700° C. to 900° C.in air for about 30 to 90 minutes; (a14) heating the substrate 114 withthe catalyst layer at a temperature ranging from 500° C. to 740° C. in afurnace with a protective gas therein; and (a15) supplying a carbonsource gas into the furnace for about 5 to 30 minutes, and growing asuper-aligned CNT array 116 from the substrate 114.

In step (a11), the substrate 114 can be a P-type silicon wafer, anN-type silicon wafer, or a silicon wafer with a film of silicon dioxidethereon. A 4-inch P-type silicon wafer is used as the substrate 114 ofthe present example.

In step (a12), the catalyst layer can be made of iron (Fe), cobalt (Co),nickel (Ni), or any alloy thereof.

In step (a14), the protective gas can be made up of at least one ofnitrogen (N₂), ammonia (NH₃), and a noble gas. In step (a15), the carbonsource gas can be a hydrocarbon gas, such as ethylene (C₂H₄), methane(CH₄), acetylene (C₂H₂), ethane (C₂H₆), or any combination thereof.

The super-aligned CNT array 116 can be approximately 200 to 400 micronsin height and includes a plurality of CNTs parallel to each other andsubstantially perpendicular to the substrate 114. The super-aligned CNTarray 116 formed under the above conditions is essentially free ofimpurities, such as carbonaceous or residual catalyst particles. TheCNTs in the super-aligned CNT array 116 are packed together closely byvan der Waals attractive force.

In the present example, the substrate 114 is fixed on a sample platform110 by an adhesive tape or a binding admixture. Alternatively, thesubstrate 114 is mechanically fixed on the sample platform 110.

In step (a2), the CNT film 118 can be formed by the following sub-steps:(a21) selecting a plurality of CNTs having a predetermined width fromthe super-aligned CNT array 116, binding the CNTs to the pulling tool100; and (a22) pulling the CNTs at an even/uniform speed to achieve theCNT film 118.

In step (a21), the CNTs having a predetermined width can be selected byusing a wide adhesive tape as the tool 100 to contact the super-alignedCNT array 116. In step (a22), the pulling direction is substantiallyperpendicular to the growing direction of the super-aligned CNT array116.

During the pulling process, initial CNTs segments are drawn out, otherCNT segments are also drawn out end-to-end due to the van der Waalsattractive force between ends of adjacent segments. This process ofdrawing ensures a successive CNT film 118 can be formed. The CNTs of theCNT film 118 are all substantially parallel to the pulling direction andconnected end-to-end.

More specifically, during the pulling process, as a thickness of the CNTsegments is not substantially equal, the thickness of the CNT filmformed by pulling is not substantially equal, and it includes aplurality of bundles with larger diameters. The bundles with largerdiameter have low light transmittance, and as a result, the CNT films118 also have low light transmittance (less than 75%).

Width of the CNT film 118 depends on the size of the CNT array 116.Length of the CNT film 118 is arbitrary and may be determined accordingto need. In the present example, when the size of the substrate 114 is 4inches, the width of the CNT film 118 approximately ranges from 1 to 10centimeters, and the thickness of the CNT film 118 approximately rangesfrom 0.01 to 100 microns.

Because the light emitted from the light emitting chips 204 has to passthrough the second CNT layer 206, the requirement for a transparency ofthe second CNT layer 206 is higher than that of the first CNT layer 202.In the method of manufacturing the second CNT layer 206, after pulledout from the CNT array 116, the CNT film 118 is treated to achievehigher transparency.

In detail, the treatment may be executed in an atmosphere comprising ofoxygen therein. In the present embodiment, the treatment is executed inan ambient atmosphere.

The treatment includes the following steps: (a) heating a part of theCNT film 118 to make partial CNTs in the part of the CNT film 118oxidized; (b) moving the CNT film 118 to make partial CNTs in otherparts of the CNT film 118 oxidized so that the entire CNT film 118 istreated.

Specifically, in the step (a), the heating may be executed using a laserdevice or a microwave generating device. For example, the laser devicemay emit laser beams with a power density of greater than 0.1×10⁴ W/m².The CNTs in the CNT film 118 absorb energy from laser irradiation andthe temperature thereof is increased. The CNT bundles with largerdiameters will absorb more energy and be destroyed. When the CNT bundlesin the CNT film 118 are destroyed due to absorbing too much energy fromthe laser irradiation, a transparent CNT film will be acquired. In thepresent embodiment, after laser irradiation, the light transmittance ofthe transparent CNT film is greater than 75%.

Furthermore, the CNT film 118 is adhesive because the CNTs haverelatively large specific areas so that the CNT film 118 can be directlyattached to the light emitting chip 204 to form the CNT layers 202, 206.More specifically, the CNT layers 202, 206 may include at least twostacked CNT films 118. An angle α between the aligned directions ofstacked CNTs in two adjacent CNT films 118 is in a range of 0°≦α≦90°.Furthermore, silver glue may be applied to joints between the twoadjacent CNT films 118 to enhance conductivity of the CNT layers 202,206.

In this embodiment, a thickness of the first CNT layer 202 is greaterthan that of the second CNT layer 206. This is because the first CNTlayer 202 needs to dissipate heat generated by the light emitting chips204.

Adhesive conductive means may be applied between the CNT layers 202, 206and the light emitting chips 204 to enhance electrical and physicalconnection strengths. The adhesive means may include silver glue andother suitable adhesive conductive means.

Referring to FIGS. 4, and 5 a-5 h, a method for manufacturing the lightemitting diode package 20, according to a second exemplary embodiment,includes steps S100 through S114.

Step S100: providing a light emitting chip structure 30 including asubstrate 32 and a light emitting layer 34 formed on the substrate 32;step S102: forming microstructures 204 b on a surface 34 a of the lightemitting layer 34; step S104: treating the light emitting layer 34 toform a plurality of spaced light emitting chips 204 on the substrate 32,a first surface 204 a of each light emitting chip 204 including themicrostructures 204 b; step S106: forming a CNT layer 206 covering thelight emitting chips 204 and forming a phosphor layer 208 on the CNTlayer 206; step S108: removing the substrate 32; step S110: forminganother CNT layer 202 on second surfaces 204 c of the light emittingchips 204, thus obtaining a first CNT layer 202 and a second CNT layer206 on opposite sides of the light emitting chips 204; step S112:forming a light reflective layer 200 on an outer surface 202 a of thefirst CNT layer 202; step S114: packaging the light emitting chipstructure 30 to obtain the light emitting diode package 20.

In step S100, the light emitting chip structure 30 is a blue-light lightemitting chip structure 30. In steps S102 and S104, referring to FIGS. 5b to 5 d, a plasma etching process may be used to form themicrostructures 204 b and the spaced light emitting chips 204. Themicrostructures 204 b include a plurality of cone-shaped grooves 204 b.When forming the spaced light emitting chips 204, a photomask 400 may bepositioned on the surface 34 a of the light emitting chip structure 30.The photomask 400 defines a plurality of through holes 402 to formpatterns on the light emitting layer 34.

In step S106, the phosphor layer 208 is a layer comprising yttriumaluminum garnet (YAG) crystal, such as an epoxy-resin layer comprisingthe YAG crystal. In step S108, the substrate 32 is removed byirradiating joints between the substrate 32 and the light emitting layer34 with a laser.

In step S110, the light emitting chips 204 may be turned upside down toform the CNT layer 202 on the second surfaces 204 c of the lightemitting chips 204. In step S112, the light reflective layer 200 is asilver reflective layer and may be formed on the first CNT layer 202 bya sputter-coating process.

In step S114, the light emitting chip structure 30 is packaged in thehousing 22. The housing 22 may be made from polymethylmethacrylate(PMMA) or epoxy resin.

Because of their good light transmittance and conductivity, the CNTlayers 202, 206 are used as electrodes of the light emitting diodepackage 20. This increases light-emitting efficiency of the lightemitting diode package 20. Furthermore, because of the plurality ofspaced light emitting chips 204 formed between the CNT layers 202, 206and flexibility of the CNT layers 202, 206, the light emitting unit 24can be conveniently bent for attaching to curved surfaces, such ascylindrical walls before packaging.

Referring to FIG. 6, a light emitting diode package 50, according to athird exemplary embodiment, is shown. The light emitting diode package50 includes a housing 52, a light emitting unit 54 received in thehousing 52.

The light emitting unit 54 includes a light reflective layer 500, afirst CNT layer 502 formed on the light reflective layer 500, a lightemitting chip 504 formed on the first CNT layer 502, a second CNT layer506 formed on the light emitting chip 504, and a phosphor layer 508formed on the second CNT layer 506.

The light emitting diode package 50 may be obtained by cutting the lightemitting diode package 20 of the first embodiment.

Referring to FIG. 7, a light emitting diode package 70, according to afourth exemplary embodiment, is shown. The difference between the lightemitting diode package 70 and the light emitting diode package 20 of thefirst embodiment is that the light emitting diode package 70 includes aplurality of spaced stripe-shaped light emitting chips 704 formed on afirst CNT layer 702.

Advantages of the third and fourth embodiments are same as those of thefirst embodiment.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present embodiments have been setforth in the foregoing description, together with details of thestructures and functions of the embodiments, the disclosure isillustrative only, and changes may be made in detail, especially inmatters of shape, size, and arrangement of parts within the principlesof the disclosure to the full extent indicated by the broad generalmeaning of the terms in which the appended claims are expressed.

1. A light emitting diode package, comprising: a housing; and a lightemitting unit received in the housing, the light emitting unitcomprising: a first carbon nanotube layer; at least two spaced lightemitting chips formed on the first carbon nanotube layer; and a secondcarbon nanotube layer covering the at least two spaced light emittingchips; wherein the light emitting unit further comprises a lightreflective layer formed on an outer surface of the first carbon nanotubelayer.
 2. The light emitting diode package of claim 1, wherein thethickness of the first carbon nanotube layer is greater than that of thesecond carbon nanotube layer.
 3. The light emitting diode package ofclaim 1, wherein each of the at least two spaced light emitting chipscomprises a light outgoing surface and microstructures formed on thelight outgoing surface, and the second carbon nanotube layer is formedon the light outgoing surfaces of the at least two spaced light emittingchips.
 4. The light emitting diode package of claim 3, wherein themicrostructures comprise a plurality of cone-shaped grooves defined inthe light outgoing surface.
 5. The light emitting diode package of claim1, wherein the light emitting unit further comprises a phosphor layerformed on the second carbon nanotube layer.
 6. The light emitting diodepackage of claim 1, wherein the at least two spaced light emitting chipsemit blue light.
 7. The light emitting diode package of claim 1, whereinthe first carbon nanotube layer comprises at least two stacked carbonnanotube films, and an angle α between the aligned directions of stackedcarbon nanotubes in two adjacent carbon nanotube films is in a range of0°≦α≦90°.
 8. The light emitting diode package of claim 1, wherein thesecond carbon nanotube layer comprises at least two stacked carbonnanotube films, and an angle α between the aligned directions of stackedcarbon nanotubes in two adjacent carbon nanotube films is in a range of0°≦α≦90°.
 9. A light emitting diode package, comprising: a housing; alight emitting unit received in the housing, the light emitting unitcomprising: a first carbon nanotube layer; a light emitting chip formedon the first carbon nanotube layer; and a second carbon nanotube layercovering the light emitting chip; wherein the first and second carbonnanotube layers are electrically conductive and a transparency of thesecond carbon nanotube layer is higher than that of the first carbonnanotube layer.
 10. The light emitting diode package of claim 9, whereina thickness of the first carbon nanotube layer is greater than that ofthe second carbon nanotube layer.
 11. A light emitting diode package,comprising: a housing; and a light emitting unit received in thehousing, the light emitting unit comprising: a first carbon nanotubelayer; at least two spaced light emitting chips formed on the firstcarbon nanotube layer; and a second carbon nanotube layer covering theat least two spaced light emitting chips; wherein each of the at leasttwo spaced light emitting chips comprises a light outgoing surface andmicrostructures formed on the light outgoing surface, and the secondcarbon nanotube layer is formed on the light outgoing surfaces of the atleast two spaced light emitting chips.
 12. The light emitting diodepackage of claim 11, wherein the first carbon nanotube layer comprisesat least two stacked carbon nanotube films, and an angle α between thealigned directions of stacked carbon nanotubes in two adjacent carbonnanotube films is in a range of 0°≦α≦90°.
 13. The light emitting diodepackage of claim 11, wherein the second carbon nanotube layer comprisesat least two stacked carbon nanotube films, and an angle α between thealigned directions of stacked carbon nanotubes in two adjacent carbonnanotube films is in a range of 0°≦α≦90°.
 14. The light emitting diodepackage of claim 11, wherein the microstructures comprise a plurality ofcone-shaped grooves defined in the light outgoing surface.